1. Field of the Invention
The present invention relates to a recording apparatus capable of multiple recording on one side or both sides of a sheet member.
2. Related Background Art
A feedback sheet transport mechanism, conventionally employed for two-side printing operation, performs an operation of bringing a print sheet, after printing on one face thereof, again to a print enabled state together with an operation of inverting the print sheet, or an operation of the image bearing face of thus already printed sheet again to the print enabled state without sheet inversion, thereby achieving multiple print in which plural prints are made on a same face of the sheet. Such sheet inversion has been achieved by stacking the sheets on an intermediate tray and re-feeding said sheets again from said tray, but such stacking and refeeding cannot be conducted simultaneously. When a printer performs a continuous two-side printing operation with a maximum throughput represented by a maximum number of prints per minute, the sheets printed on one faces thereof will be transported to the intermediate tray with said speed. On the other hand, since the intermediate tray cannot simultaneously perform the stacking of the print sheets and the refeeding thereof, it has to preferentially stack the print sheet fed from the upstream side and to conduct the refeeding of the print sheets, in interim periods, for transfer to the printer, in order to avoid sheet jamming.
On the other hand, the sheet refeeding operation cannot be interrupted once it is started. Consequently such refeeding operation has to be completed within a period from the completion of a preceding stacking operation to the start of a succeeding stacking operation. Situation is substantially same in a multiple printing operation. More specifically the refeeding has to be conducted, from the completion of a preceding stacking operation, within a period equal to the sum of a time corresponding to the sheet size and a time corresponding to the interval of the sheets.
However, in a situation where a relation: EQU t.sub.s &gt;(t.sub.0 +t.sub.1) (1)
stands, wherein t.sub.s is the stacking time of the intermediate tray, while t.sub.0 is the time corresponding to the sheet size acceptable in the printer, and t.sub.1 is the time corresponding to the interval between the sheets, the intermediate tray can only conduct the stacking operation and will eventually overflow, so that the two-side printing operation can never be achieved, and the maximum throughput, determined by the stacking time t.sub.s of the intermediate tray, is reduced.
On the other hand, in a situation where a relation: EQU t.sub.s &lt;(t.sub.0 +t.sub.1) (2)
stand, the number of sheets discharged to the intermediate tray exceeds that of sheets fed therefrom unless the interval of re-fed sheets is equal to that of the sheets supplied from the printer, so that the interval of the print sheets fed from the feedback transport mechanism becomes inevitably longer. Thus there may result an inconvenience that the recording apparatus, of a lower hierarchy in a system, may govern the operation of an external equipment of a higher hierarchy.
Also in a situation where said relation (2) stands, in addition of elongation of the interval of the re-fed sheets in comparison with the interval of sheets supplied to the intermediate tray, the number of sheets supplied to the intermediate tray significantly exceeds the number of sheet refed therefrom if two-side continuous printing operation is continued, eventually causing an overflow and sheet jamming in the intermediate tray.
Furthermore, because of the limitation that the intermediate tray cannot simultaneously effect the stacking of the printing sheets and the sheet feeding, a random sheet feeding from the feedback transport mechanism or a sheet source is not possible and the throughput is therefore significantly lowered.